The present invention generally relates to implanted medical devices (IMDs) and instruments. Specifically, the invention relates to a graphic user interface (GUI) in which disruptions in the displayable ECG data stream are highlighted using color-coded schemes to indicate communication channel disruption and problems with displayable data quality, collected from medical devices. More specifically, the invention is compatible with and adaptable to a network in which various medical devices communicate and exchange clinical data across various network systems.
IMDs are implanted to treat and/or monitor a variety of patients who have a variety of individual or multiple medical conditions. Such IMDs may include, without limitation, drug pumps, nerve stimulators, cardiac defibrillators, and cardiac pacemakers. Once implanted, many of these IMDs require the downloading of data, collected and stored by the IMD, to a medical instrument, usually a programmer. Based on these data, the IMD may be reprogrammed and/or reinterrogated to ensure operational parameters that are appropriate to the patient.
Programmers are instruments that downlink to the IMD as well as receive an uplink from the IMD. These programmers use customized software that can be characterized as a windowing environment with overlapping windows and a GUI using multiple colors. The windowing environment makes the customized software familiar to the user. One of the important aspects of a GUI is its use of color or other forms of distinctive notice to highlight and call the user""s attention to certain portions of the screen or to clarify and segment specific pieces of information.
Electrocardiogram (ECG) and/or intracardiac electrogram (EGM) signals are often the only few continuous data stream of graphic information presented on a programmer screen. The ECG tracing is essentially nothing more than a continuous time-dependent graph of the QRST complex as seen by external leads attached to the skin. The EGM, on the other hand, is a representation of the same complex as seen by the implanted lead(s). ECGs are used to monitor the patient""s cardiac conduction system as well as the delivery of the therapy specific to the IMD. When a programmer of the type disclosed in U.S. Pat. No. 5,345,362 issued to Winkler, et al., incorporated herein in its totality, is used, a physician may select various colors on the programmer screen to differentiate one cardiac vector from another, as well as segmenting the ECG from the intracardiac EGM.
Typically, a programmer used during a telemetry procedure is positioned remotely from the patient. The programming head of the programmer, containing at least an antenna, is connected to the body of the programmer via a stretchable coil cable. The programming head is positioned over the patient""s implanted device site for programming or interrogating the implanted device. The programmer typically consists of one or more microprocessors and contains a programmable memory capable of storing executable programs under the control of the operator via a user interface, e.g., the programmer""s screen. The IMD may receive command instructions from the programmer. Such command instructions are referred to as downlink transmissions, i.e., transmissions from the external device or programmer to the IMD. Typically, the downlink transmissions may include program instructions or steps for directing the operation of the IMD.
The downlink instructions may also request a data dump of programmed parameters and diagnostic data. Such transmissions are typically referred to as uplink transmissions, i.e., transmissions from the implantable medical device to the external device. In other words, in addition to transmitting commands, the programmer may receive and transmit data from the IMD. At times, communication between the IMD and the external instrument may be limited to transmissions by only one of the devices with the other device receiving those transmissions. Alternatively, communication between the IMD and the external instrument may include transmissions to and by both devices.
The communication between the IMD and the external instrument, e.g., programmer, is facilitated by receiving and transmitting circuitry included within the implanted medical device and the external device. The implanted medical device includes a receiver and transmitter circuitry that may cooperate with other circuitry of the IMD to receive commands from and transmit data to the external instrument. Further, the external instrument includes transmitting and receiving circuitry for communicating with the implanted medical device. Both the IMD and the external instrument include antenna structures coupled to the receiver and transmitter circuitry for transmitting and receiving RF/telemetry signals.
Various systems for performing telemetry with regard to implanted devices are known. For example, such systems are described in U.S. Pat. No. 5,127,404 issued to Wyborny, et al.; U.S. Pat. No. 4,556,063 issued to Thompson, et al.; U.S. Pat. No. 5,342,408 issued to de Coriolis et al.; and U.S. Pat. No. 5,752,976 issued to Duffin, et al.: International Application, WO 01/03575 A1, System for Remote Communication with an Implantable Medical Device by Ferek-Petric, all incorporated herein by reference in their entirety.
Errors may occur in all communication systems. A variety of techniques have been developed to detect such errors and, when possible, correct them. For example, in a standard local area network, such as Ethernet, error detection mechanisms, such as cyclic redundancy codes (CRC) are implemented at various levels of protocol.
In wireless local area networks, the bit error rate of a transmission is affected by a number of factors not present in a classic wired LAN. Thus, the bit error rate of a given transmission depends on the amount of power transmitted, the process by which the receiver receives that power, the presence of noise and/or interference, and the quality of the transmission once it reaches the receiver. In addition, there are a number of sources of interference that may be encountered in such systems. For example, for systems transmitting in the industrial, scientific and medical (ISM) band, around 2.4 GHz, as regulated by the Federal Communications Commissions (FCC) Part 15 Regulations, interference may arise from other sources within the same band, such as microwave ovens, security systems and car alarms. Also, additive white gaussian noise, thermally generated naturally, may be a source of interference. Further, these types of interference may occur even after a user has been allocated a channel for communicating. Thus, a data packet may be corrupted early or late in a transmission sequence. Relying on the standard CRC techniques in local area network packets alone may be insufficient in these environments. For instance, CRC can detect burst errors up to the length of CRC itself. In wireless environments, burst errors can be significant portions of packet length, entire packets, or multiple packets.
Patients with IMDs require periodic monitoring, which can be within a clinic or hospital setting, or from a remote setting, e.g., from a patient""s home. Within the clinic or hospital setting, a physician or clinician is typically present and interacts with the programmer directly. Any interruption in the data stream can be quickly identified and addressed by qualified medical personnel under most circumstances. For example, a short interruption in the ECG tracing should be apparent, unless the physician/clinician""s attention to the programmer screen is also interrupted. However, even if the user""s attention has not wavered, a pause in the ECG tracing might easily be confused with a physiologic cause, inter alia, sinus pause or sinus arrest. But, due to the close attendance of a qualified medical technician, the situation can be quickly diagnosed and any corrective action, if necessary, be taken. Still, it would be advantageous to have a system by which medical personnel can quickly differentiate between pauses on the ECG tracing due to a mechanical, electrical, telemetric disruption and one due to a physiologic condition in the heart.
The situation may be entirely different when monitoring takes place from a remote environment via wireless technology. Patients live in various locations, including remote places, such as islands, mountainous areas, or places where travels may be difficult at all times or at only specific times of the year. Moreover, regardless of where the patient may live, the attending physician may, at times, desire additional input from the IMD for subsequent programming. Thus, rather than have the patient travel to the clinic, he may request a remote monitoring session. During any remote monitoring session, it can be very difficult for the technician to determine whether any interruption in the ECG tracing is mechanical or physiologic. Thus, it would be an improvement in the art to have a system that makes such a differentiation. Accordingly, it is desirable to provide a method for detecting errors in wireless data transmissions relating to medical device communications, which is robust in the presence of various sources of interference or noise.
The present invention provides apparatus and method for detecting errors in a network communication channel that comprises a medical instrument such as a programmer that receives an ECG data stream from at least one IMD during a programming procedure. The networks to which the programmer is attached have sufficient throughput to transfer the ECG data stream to provide a high quality ECG tracing. There is, however, the potential for temporary interruptions of the data stream signals when these pass through network hubs, concentrators, and routers. Such interruptions may result in a loss of the ECG signal. Generally this loss of signal may last for only a fraction of a second. As such, the momentary loss of signal usually has a negligible impact on clinical and diagnostic practice when an experienced practitioner staffs the programmer. Nonetheless, an inexperienced clinician may be confused by the momentary pause in the ECG tracing.
The ECG data stream may be transferred via UDP (User Diagram Protocol) data packets with error detection codes, such as cyclic redundancy codes, imbedded within the data packets as is disclosed in U.S. Pat. No. 5,745,479 issued to Burns, et al., and incorporated herein by reference in its totality. The present invention, however, discloses an alternative error detection scheme that recognizes interruptions in the flow of UDP data packets. Processing software in the programmer is responsive to the interruption within the transmission of UDP data packets to detect errors.
The wireless communication channel in the programmer has a wireless link to a standard local area network. The UDP packets are transmitted from the IMD preferably using a radio frequency communication band, having a frequency on the order of 2 to 5 GHz. The UDP packets are transmitted from the IMD to the programmer, which includes software for identifying pauses in the received signal that are typical of erroneous data. The present invention provides client software that detects errors based on the interruption in the flow of UDP packets. When such an interruption occurs, the programmer""s GUI software changes the color of the ECG tracing during the time of signal interruption.
The present invention will now be described with reference to the following drawings, in which like reference numbers denote the same element throughout.